After a string of negative press sent its reputation spiraling in recent months, United Airlines UAL, +0.53% is being hit with another blow from the Federal Aviation Administration (FAA), which is proposing a $435,000 civil penalty against the company for operating a plane “not in airworthy condition” nearly two dozen times.

“At United, the safety of our customers and employees is our top priority,” a United Airlines spokeswoman told MarketWatch. “We took action after identifying the issue and are working closely with the FAA in their review.”

The FAA alleges United didn’t perform a required inspection of a Boeing 787 after replacing its fuel pressure pump on June 9, 2014. It operated 23 domestic flights before completing the required inspection on June 28, 2014. Two of those flights occurred after the FAA notified United it had not performed the required inspection, it claims, and during all 23 flights the aircraft was “not airworthy.”

“Maintaining the highest levels of safety depends on operators closely following all applicable rules and regulations,” FAA administrator Michael Huerta said in a statement. “Failing to do so can create unsafe conditions.”

The FAA also announced in 2016 that it would require airlines to implement safety management systems by 2018. Brett Snyder, author of the airline-industry blog CrankyFlier.com, said it is important to note that “not airworthy” doesn’t necessarily mean unsafe.

Had United done the correct inspection, “it most likely would have found that the work was done correctly and it would have been able to fly just as it did even without the inspection,” he said. “But inspections are mandated for a reason: to ensure that the work is done properly every time.”

It is currently safer to fly than ever before, according to trade organization Airlines for America. Airlines safely operate 27,000 flights to more than 800 destinations a year, a spokeswoman from the organization said, delivering more than 2 million passengers each day. United will reportedly meet with the FAA to discuss the fines proposed this week.

“The airlines continue to lobby for less regulation and more power and this is the result,” Kate Hanni, founder of passenger-rights group Flyers Rights said. “They demonstrate over and over again that they cannot maintain even the most basic standards of safety for their passengers or their aircraft.”